Ok so heres the steps I took tonight...
First, I made a new mount for the Z-axis motor. Mine was not lined up right - when the allthread was in the bearing, you could see the coupler bending - the hole for the bearing was not centered right. So I made a new one (laser cut wood) and that solved THAT problem (coupler was straight once all mounted).
But I'm still binding. So I tried speed tests... I didnt mess with the F command I just set the $5 (default seek rate) down to 200 from 1100 - and it didnt bind, but the motor stuttered. You can see it in this video:http://www.youtube.com/watch?v=WpkNmMMUi6U
What the video shows is a stutter going up, then a stutter going down (at lower speeds the motor does this even when not in the mount - bad motor?).
The third movement in the video is after I set the speed back to $5=1100 so you can see the binding. It accelerates and hits top speed and binds.
When turning the allthread by hand, you can feel it get hard to turn as it reaches a point in it's off-center-ness (if spinning free of the delrin nut it whips - and I cant center it to save my life - may try buying a new rod).
Any thoughts on both the stuttering, and the binding?
(Edit: And yes, the mount plate is NOT on tight - thats why it rocks. I thought loosening it might help the binding as the motor had room to wiggle. Nope. Still bunds. But you can see by just how much it's wiggling just how badly my rod is off center, whipping, causing the binding).